1. Field
Implementations described herein generally relate to semiconductor manufacturing and more particularly to the process of plasma etching an amorphous carbon layer.
2. Description of the Related Art
As the feature size of the device patterns get smaller, the critical dimension (CD) requirement of features becomes a more important criterion for stable and repeatable device performance. Allowable CD variation across a substrate has also scaled with the scaling of feature CD. With lateral dimensions scaling faster than vertical dimensions, because of issues such as device capacitance, high aspect ratios (HAR) are now prevalent in the industry. When such demanding aspect ratios and CD control are compounded with requirements of high etch selectivity, sidewall smoothness and high tool throughput, the process window for any hardware configuration can become very small. In many situations, a small process window can be found only when a number of process gases are incorporated into a complex etchant gas mixture combined with extreme hardware settings, such as very high RF bias powers, to achieve a fragile balance between sidewall passivation, etch rate and mask selectivity. However, such small process windows typically suffer from performance limitations which cannot be tuned out of the etch process with known means.
Fabrication techniques often now employ a mask stack that includes non-photo definable material layers disposed below a photo definable layer (i.e., a photoresist). The non-photo definable material layers may include a carbonaceous layer, which may be of an inorganic material comprising at least 20 wt % carbon. Amorphous carbon, typically comprising greater than 50 wt % carbon and low-k dielectrics comprising at least 20 wt % carbon content are included in this class of materials. One example of such a carbonaceous material is available from Applied Materials, Inc. of Santa Clara, Calif. under the name of ADVANCED PATTERNING FILM™ (APF).
Highly reactive oxygen plasma is typically used to etch and pattern the amorphous carbon layer. However, as feature sizes decrease and aspect ratios increase, these highly reactive oxygen plasmas lead to the formation of oxide deposits (e.g., silicon oxide) which often clog or block the top CD causing the etch rate to slow and eventually stop. Currently, oxide deposits are removed using fluoride containing chemistries; however, these fluoride containing chemistries often damage the sidewall passivation present on the amorphous carbon film leading to big bow profiles.
Therefore, there is a need for new processes for etching amorphous carbon films.